The present invention relates to a surface acoustic wave filter having interdigitalized fingers, and more specifically to a small-size high-performance high-frequency filter required for radio communication devices, at a high productivity as a transducer for exciting or receiving a surface acoustic wave (hereafter referred to as a SAW).
A known high-frequency filter combines a coil and a capacitor. Recently mobile radio communication devices employ cascade connecting dielectric resonators instead of the coil and capacitor for necessary frequency characteristics. However, there is a major objective to downsize such a high-frequency filter to make it suitable for a mobile radio communication terminal, which is strongly desired, because the type of circuit is a hybrid circuit or three-dimensional circuit.
A filter using SAWs is superior for mass productivity, because it is small in size and it can be produced by semiconductor process techniques. The prior art filter using SAWs is inferior to a conventional dielectric resonator type filter in view of the pass band loss and a steep cutoff frequency characteristic between the pass band and a stop band, however.